Diplodus spp. assemblages on artificial reefs: importance for near shore fisheries F. LEITA ˜ O & M. N. SANTOS Instituto Nacional dos Recursos Biolo ´gicos (INRB/L-IPIMAR), Olha ˜o, Portugal K. ERZINI Universidade do Algarve, Campus de Gambelas, Faro, Portugal C. C. MONTEIRO Instituto Nacional dos Recursos Biolo ´gicos (INRB/L-IPIMAR), Olha ˜o, Portugal Abstract Artificial reefs have been deployed along the southern coast of Portugal (Algarve) since 1990 to enhance artisanal fisheries. The objectives of this study were to: (1) describe the colonisation process; (2) assess the role of the artificial reefs in terms of juvenile recruitment and growth and as mating/spawning areas and (3) evaluate the potential of artificial reefs as near shore artisanal fishing grounds for three economically important fish species, Diplodus bellottii (Steindachner), Diplodus sargus (L.) and Diplodus vulgaris (Geoffroy Saint-Hilaire). The fish assemblages were monitored after the deployment of a large artificial reef (Faro/Anca˜o) in 2002. Colo- nisation rates for the three species were fast. Artificial reefs play a multiple role for Diplodus spp., acting as recruitment, growth and nursery areas for juveniles, and spawning/mating areas for adults, and can thus be considered essential fish habitat. Three months after deployment of the artificial reefs, exploitable biomass was 16, 29 and 8 kg per reef group, respectively, for D. bellotti, D. sargus and D. vulgaris. These results indicate that artificial reefs quickly become good fishing grounds, where suitable financial yields may be obtained by fisher. Moreover, the artificial reefs became new and alternative fishing grounds, allowing reduction of fishing effort over traditional rocky areas that are scarce along the Algarve coast. Management measures for artificial reefs, in terms of fishing strategies, are discussed. KEYWORDS: artificial reefs, Diplodus spp., exploitable biomass, fishery management. Introduction The deployment of artificial reefs in European waters has increased considerably over the last 30 years (Jensen 2002 and references therein). Fisheries enhancement, increasing diversity and protection/ mitigation of marine habitats are among the different arguments used to justify the creation of these artificial habitats (Jensen, Collins & Lockwood 2000). On the southern coast of Portugal (Algarve), multi-purpose artificial reefs have been deployed since 1990. Their deployment aims to enhance the amount of hard bottom habitat, which is scarce on the sandy southern grounds, to provide suitable habitat for fish and to increase fishing yields (Monteiro & Santos 2000). The idea behind the deployment of artificial reefs for fishery enhancement relies on the assumption that habitat is a limiting factor and that artificial reefs will provide critical habitat to promote the produc- tion of new biomass through increased growth and survival of juveniles (Bohnsack 1989). Nevertheless, if artificial reefs act like attraction devices, increasing fish density, then higher density may increase catch- ability, and the greater accessibility increases fishing Correspondence: Francisco Leita˜o, IPIMAR, Avenida 5 de Outubro s/n, P-8700-305 Olha˜o, Portugal (e-mail: fleitao@cripsul.ipimar.pt) Fisheries Management and Ecology, 2009, 16, 88–99 doi: 10.1111/j.1365-2400.2008.00646.x Ó 2009 Blackwell Publishing Ltd. Fisheries Management and Ecology